In an electrically controlled throttle apparatus shown in FIGS. 22 and 23, a driving device such as a motor controls an opening degree of a throttle valve 102 in accordance with a position of an accelerator pedal stepped by a driver. In the throttle apparatus, a gap is formed between a bore inner periphery of a substantially tubular throttle body 101 and an outer circumferential periphery of a throttle valve 102, and the gap has a large influence of an airtightness of the throttle apparatus when the throttle valve 102 is in its full close position.
Conventionally, the throttle body 101 and the throttle valve 102 are independently manufactured in each different processes. Subsequently, a manufactured throttle valve 102 is combined with a manufactured throttle body 101 in accordance with an inner peripheral dimension of the manufactured throttle body 101 in a downstream process. Alternatively, a manufactured throttle body 101 is combined with a manufactured throttle valve 102 in accordance with an outer circumferential dimension of the throttle valve 102 in a downstream process. Thus, a predetermined gap is obtained between the bore inner periphery of the throttle body 101 and the outer circumferential periphery of a throttle valve 102. A throttle shaft 103 integrally rotates with the throttle valve 102. Both of the ends of the throttle shaft 103 are rotatably supported by cylindrical valve bearings 104 provided in the throttle body 101.
In molding methods according to JP-A-5-141540 and JP-B2-3315135, a manufacturing process of the throttle body and the throttle valve is reduced. In the molding methods, the throttle body 101 and the throttle valve 102 shown in FIG. 24 are integrally molded of a resinous material in the same molding dies. At first, the substantially tubular throttle body 101 is integrally molded of a resinous material. Subsequently, inner periphery (bore inner periphery) of the throttle body 101 is used as a part of a molding die molding the throttle valve 102, and the throttle valve 102 is molded. Thus, a shape of an outer circumferential periphery of the throttle valve 102 is adapted to a shape of the bore inner periphery of the throttle body 101 in the above molding methods.
FIGS. 25A to 25C are cross-sectional views showing molding process of the throttle valve 102 in the throttle body 101 using the above molding methods. The throttle body 101 is molded of a resinous material in a body cavity formed in a fixed dies 111, 112 and a moving die 113 (FIG. 25A). The molded throttle body 101 is gradually cooled in the body cavity to be solidified. Subsequently, the movable die 113 is slid to its backward position in order to form a valve cavity, into which a resinous material is filled (FIG. 25B). The throttle valve 102 is molded of a resinous material in the throttle body 101 (FIG. 25C).
However, in this molding process, the throttle body 101 is partially used as a molding dies for molding the throttle valve 102. Therefore, the throttle body 101 and the throttle valve 102 cannot be simultaneously molded in one molding process, that is, sequential molding process is needed. Besides, the throttle body 101 needs to be cooled and solidified in the molding dies before molding the throttle valve 102, and this molding process needs a cooling period. Accordingly, the molding process becomes long. Besides, thermal cycle may be degraded due to the cooling process of the throttle body 101 received in the molding dies. Furthermore, the outer circumferential periphery of the throttle valve 102 may weld to the throttle body 102 in the outer circumferential periphery of the throttle valve 102.